Volume 22 • Issue 05 • 2018
cheeses and butter contain very little Lactose.
These dairy products can as a result be consumed
by Lactose-intolerant individuals without causing
discomfort.
WHY LACTOSE?
In the case of sour milk, Lactose is broken
down by bacteria (that have the enzyme
β-galactosidase) into Glucose and Galactose that
is fermented into lactic acid. Even though yoghurt
still contains Lactose, the levels of Lactose is
reduced sufficiently through fermentation to not
cause symptoms in most people with Lactose-
intolerance. Newborn mammals have sufficient sup-
plies of lactase to digest the Lactose in
milk. As the baby matures the produc-
tion of lactase starts to decline. This
leads to undigested Lactose ending up
in the large colon, which in turn leads to
bloat, flatulence, discomfort and diar-
rhoea. Partly due to the osmotic effect of
Lactose and partly due to bacteria in the
colon fermenting Lactose and producing
gas in the process.
Because Lactose is a major osmole in milk,
accounting for approximately 50% of milk’s
osmolality, its levels tend to remain stable in
milk. Any change in the Lactose levels need to
be considered as significant and need to be
investigated The question arises as to why did na-
ture settle on Lactose instead of one of
the simpler sugars such as Glucose or
Sucrose? One theory postulates that it
is because it takes a lot of energy for
a mother to breastfeed as well as sus-
tain her own energy levels. Should she
become pregnant while still breastfeed-
ing, her reserves will be diverted to the
developing foetus at the expense of
producing breastmilk. This will decrease
the chances of survival of the child being
breastfed.
Although goats milk only has approximately 10%
less Lactose than cow’s milk, countless people
with Lactose-intolerance can consume goat’s milk
without adverse effects. The reason is not quite
clear
WHAT AFFECTS LACTOSE LEVELS
IN COW’S MILK?
Lactose is the primary osmole in milk. Anything
that affects Lactose production will affect milk
yield.
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Lactose is quite insensitive to changes in
diet composition. Underfeeding being the
only part of diet that affects Lactose levels.
Lactose is made from Glucose which acts as
an energy source of the cow. If total energy
and dry matter intake is restricted (or
low quality forage is used) it will lead to a
reduction in Lactose production.
Lactose levels drop towards late lactation
There is a slight day to day variation in
Lactose levels of approximately 0.07 - 0.09
percentage units
Stress can reduce Lactose levels
There is a high correlation between a high
SCC (Somatic cell count) and reduced
Lactose levels. Low Lactose levels is a very
accurate predictor of subclinical mastitis.
Anything that addresses the above points will
improve milk production by increasing the
lactose production.
While a mother is breastfeeding there
is a negative hormonal feedback which
suppresses ovulation and hence her
chances of falling pregnant. This gives
the suckling offspring sufficient time
to develop to the stage where it can
consume solid foods. At that stage the
lactase activity starts to decline, causing
discomfort for the offspring whenever
it breastfeeds. This discomfort aids in
weaning the child. After weaning the
negative hormonal feedback disappears
and the mother starts to ovulate again.
The conclusion is that Lactose is
nature’s way of regulating the time
between pregnancies to optimise the
frequency of reproduction, without
endangering the chances of survival of
any of the offspring.
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